Optimization and therapeutic valorization of the symptomatic treatment of alzheimer&#39;s disease with rivastigmine, galantamine or donepezil, by selected aminotetrahydrofurans acting as mixed sigma-1 / muscarinic ligands

ABSTRACT

The present invention involves the selected aminotetrahydrofurans AE37, AE37Met, AE14 and their enantiomers as original mixed sigma-1/muscarinic ligands for the optimization of the anticholinesterasic drugs and more specifically of Donepezil, Galantamine or Rivastigmine. Indeed, these aminotetrahydrofurans exhibited M2 and M3 muscarinic antagonisms against the cholinergic adverse effects of these drugs, which constitute the most limitating factor in the use of these drugs against the symptoms of the Alzheimer&#39;s disease (AD). Moreover, by their antagonism of the presynaptic muscarinic M2 cholinergic autoreceptors and their very selective sigma-1 agonism they constitute putative agents for the valorization of the anticholinesterasic drugs and more specifically of Donepezil, Galatamine or Rivastigmine from their present status of drugs acting against the symptoms of AD to the perspective of therapeutic agents against the evolution of AD.

The present invention involves the original mixed sigma-1/muscarinic ligands: terahydro-N,N-dimethyl-2,2-diphenyl-3-furanomethanamine (AE37), its isomer tetrahydro-N,N-dimethyl-5,5-diphenyl-3-furanomethanamine (AE14), their enantiomers and the unique metabolite of AE37, tetrahydro-N-methyl-2,2-diphenyl-3-furanomethanamine (AE37Met) and its enantiomers as -1) optimization agents of the symptomatic treatments, with inhibitors of acetylcholinesterase (IACEases) Donepezil, Galantamine of Rivastigmine, of Alzheimer's disease (AD). And -2) as valorization agents of the IACEases as the therapeutic drugs, i.e., capable to stop or, at least, to strongly slowing the evolution of Alzheimer's disease (AD). Indeed, in spite of some encouraging effects of Donepezil, Galantamine and Rivastigmine on the symptoms of mild to moderate AD, no significant therapeutic impact of these IACEases on the evolution of AD was obtained and number of clinical studies re-ported worsening of the patients AD treated with the above drugs compared with patients AD treated with placebo.

Moreover, the positive effects of symptomatic treatments with Donepezil, Galantamine or Rivastigmine, on mild to moderate AD symptoms, were obtained at high oral doses (10 or even 23 mgs/day, for Donepezil, 12 mgs/day, for Rivastigmine, given also at 13.3 mgs/day, by transdermal patch and 24 mgs/day for Galantamine), on memory, thinking or quality of life and were usually accompanied by several cholinergic adverse effects : nausea, vomiting, diarrhea, bradycardia.

The aforementioned aminotetrahydrofyrans: AE37, AE37Met, AE14 and their enantiomers, were extensively studied and were confirmed as mixed sigma-1/muscarinic ligands which, by their pharmacological (molecular, ex-vivo and in vivo) profile, are indicated as optimization agents of the symptomatic treatments of AD with the aforementioned IACEases. Indeed, all these aminotetrahydrofurans are antagonists of the M2 and M3 muscarinic receptors which originate the cholinergic side effects of Rivastigmine, Galantamine and Donepezil. More specifically, AE37, which was clinically studied in Phase Ia, could suppress the aforementioned side effects at 1 to 10 mgs, oral/day or higher dose, if necessary, allowing the use of elevated and efficient doses of all these IACEases.

All these aminotetrahydrofurans exhibited anti-amnesic effects in the tests of scopolamine, dizocilpine and against the amnesia induced by intracerebral injection of soluble amyloids Aβ25-35, in mice. AE14 exhibited also promnesic activity in the step-down test, on mice.

According to the molecular pharmacologic profiles, with the ex-vivo functional tests and the in vivo antagonisms of the aforementioned anti-amnesic effects of these aminotetrahydrofurans, their anti-amnesic activity originated by the synergy between the selective sigma-1 (vs sigma-2) agonistic component of these molecules and their antagonism of the presynaptic M2 muscarinic auto-receptors activating the release of acetylcholine on the M1 postsynaptic muscarinic receptors [1]. These two anti-amnesic components are very important, if associated, in administration with Rivastigmine, Galantamine or Donepezil, for the valorization of the IACEases as therapeutic agents capable to stop or, at least, to strongly slowing the evolution of AD. Indeed, the aforementioned results showed that these aminotetrahydrofurans protected the neurons against the stress induced in the Endoplasmic Reticulum (ERstress), i.e., against protein misfolding, mitochondria dysregulation, generation of neurotoxic species and apoptosis, principally, by their selective sigma-1 (vs sigma-2) agonism in concert with their M2 auto-receptors antagonism, indusing cholinergic release. ER stress occurs normally with ageing and pathologically in neurodegenerative diseases, as AD. Sigma-1 agonistic activity of these aminotetrahydrofurans is, therefore an interesting component for the clinical valorization of the IACEases as therapeutic agents acting against the fatal evolution of AD.

Concerning Donepezil, which exhibited a high sigma-1 agonism, the synergy with the aminotetrahydrofurans is interesting in a different viewpoint. The proposed aminotetrahydrofurans are very selective sigma-1 (vs sigma-2) receptors ligands: AE37 derivatives have not any sigma-2 affinity and AE14 derivatives are, at least, 250 fold more selective for sigma-1 receptors (vs sigma-2).

The author found intriguing the absence of therapeutic effects of Donepezil against the evolution AD and the existence of worsening reports, as Donepezil was, in the past decade, presented as selective sigma-1 ligand, in addition to its IACEase proper-ties. As he did not found any data on the sigma-2 affinity of Donepezil, he confided this test to CEREP (France) and obtained results suggesting an IC50=250 to 300 nanoM for simga-2 receptors ‘2’. There is mounting evidence that sigma-2 ligands are usually (but not always) proapoptotic and, therefore, putative anticancer drugs. In this context, Donepezil was recently studied as putative anticancer drug alone or in synergy with clinically used anticancer drugs. Another molecular aspect which possibly augmented the risk of pro-apoptotic activity of Donepezil, particularly at high doses, is the similarity it exhibited with Irinotecan, an anticancer drug, in 3D structural studies [3]. In spite of a possible putative use of Donepezil as anticancer drug, these particularities of Donepezil and specifically its sigma-2 affinity could originate apoptosis of neurons, cancel the positive effects of the drug and explain the absence of therapeutic effect on AD.

The aforementioned observations suggested that the synergy with the proposed aminotetrahydrofurans are interesting for Donepezil, even in the sigma-1 agonistic domain allowing the obtention of higher sigma-1 selectivity and anti-apoptotic activity.

More importantly, the increase of acetylcholine on presynaptic muscarinic M2 auto-receptors, induced by the IACEases (Rivastigmine, Galantamine or Donepezil) is deleterious for the cholinergic neurons and for all the neuronal systems modulated by the extrasynaptic M2 receptors (especially in AD and in ageing, where these M2 auto-receptors are hyper-activated by neurotoxins and soluble amyloids [4]) and could be the most important factor explaining the absence of the therapeutic effects of these drugs on the evolution of AD and also their weak effects against the AD symptoms. Indeed the high concentrations of acetylcholine, induced by the IACEases Galantamine, Rivastigmine and Donepezil, hyper-stimulated the M2 auto-receptors which exerced high inhibition of the released acetylcholine and severe hypo-activity of the presynaptic cholinergic neurons therefore inducing, in a first phase, the diminution of the cholinergic effect on M1 and nicotinic receptors (insufficient symptomatic benefit) and, in a second phase, degeneration of hypoactive cholinergic neurons (absence of therapeutic effects on the evolution of AD and, possibly, even worsening).

In this context, the preferential antagonism of the M2 cholinergic auto-receptors by these aminotetrahydrofurans (especially of the AE37 group) could be considered as an important positive synergestic factor, in concert with their sigma-1 selective agonistic activity, for the therapeutic valorization of Galantamine, Rivastigmine and Donepezil.

It is noteworthy that in the acute experiments of co-administrations of these aminotetrahydrofurans and Donepezil, in protocols of amnesia, in mice, with scopolamine or dizocilpine, no significant synergistic effects were observed. On the contrary, in the sub-chronic neurodegenerative amnesia, in mice, by intra-cerebral injection of soluble amyloids Aβ25-35, potentiations (i.e., more than synergistic effects) were obtained with AE37 plus Donepezil. These results confirmed that this antagonistic effect on the cholinergic auto-receptors M2 is an important, if not decisive, factor in the valorization of the activity of Donepezil by AE37. Indeed, in the acute scopolamine and Dizocilpine amnesia experiments, in mice, no synergy was observed because Donepezil has the two components of AE37 i.e., sigma-1 and cholinergic (via IACEase foe Donepezil and by M2 auto-receptors antagonism for AE37). However, in the AB25-35 sub-chronic neurodegenerative amnesia, in mice, (i.e., in AD like conditions) the antagonism of auto-receptors M2 appeared decisive in the AE37 potentiating effects developed in concert with a more selective sigma-1 effect, reinforced by AE37), which reflect the anti-neurodegenerative valorization of Donepezil by AE37.

Finally, especially for the AE37 derivatives, their anti-NMDA activity (i.e., protection against the glutamatergic toxicity which induced degeneration of neurons via the action of the neurotransmitter glutamic acid on N-Methyl-D-Aspartic acid (NMDA) receptors of the brain) is a putative ameliorating component in the synergistic therapeutic valorization on the IACEases.

REFERENCES

-   [1] Alexandre VAMVAKIDES, Brevet d'Invention No 0601577 France, 20     Jul. 2012 and W02008/087458. -   [2] CEREP Report 100005726, 18 Oct. 2012. -   [3] Harel M. et al., Mol. Pharmacology: 67. 1874-81, 2005.

[4] Liu J. et al., J. Biol. Chem., 284, 19564-71, 2009. 

1. Pharmaceutical use of the original mixed sigma-1muscarinic ligand tetrahydro-N,N-dimethyl-2,2 diphenyl-3-furanomethanamine (AE37), its isomer tetrahydro-N,N-dimethyl-5,5-furanomethanamine (AE14), the unique metabolite of AE37, tetrahydro-N-methyl-2,2-diphenyl-3 -furanomethanamine (AE37Met), their enantiomers and their pharmacologically acceptable salts as optimization agents of the symptomatic treatments of the Alzheimer's disease (AD) by the inhibitors of cholinesterases (IChEases) and also in the valorization of the IChEases as therapeutic drugs against AD.
 2. All pharmacological compositions characterized by the fact that they do contain compounds of the claim 1 and, at least, one pharmaceutically acceptable excipient.
 3. Pharmaceutical use of the compounds of the claim 1 against the cholinergic adverse effects of the IChEases, in the symptomatic treatment of AD, by the antagonism of the M2 and M3 muscarinic receptors exerced by the compounds of the claim
 1. 4. Pharmaceutical use of the compounds of the claim 1 for the valorization of IchEases as therapeutic agents against the evolution of AD, by the antagonism of the pre-synaptic muscarinic M2 autoreceptors in synergy with their sigma-1 selective agonism exersed by the compounds of the claim
 1. 5. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) against the adverse cholinergic effects of Donepezil (orally 5, 10 or even 23 mgs/day) in the symptomatic treatment of AD, by their antagonism of the M2 and M3 muscarinic receptors.
 6. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) for the valorization of Donepezil (orally, 5, 10 or even 23 mgs/day) as therapeutic drug against the evolution of AD, by their antagonism of the presynaptic muscarinic M2 autoreceptors in synergy with their sigma-1 selective agonism.
 7. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) against, the adverse cholinergic effects of Rivastigmine (orally, 6 to 12 mgs/day or transdermal patch 4.6, 9.5 or 13.3 mgs/day), in the symptomatic treatment of AD, by their antagonism of the M2 and M3 muscarinic receptors.
 8. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) for the valorization of Rivastigmine (orally, 6 to 12 mgs/day or transdermal patch 4.6, 9.5 or 13.3 mgs/day) as therapeutic drug against the evolution of AD, by their antagonism of the presynaptic muscarinic M2 autoreceptors in synergy with their selective sigma-1 agonism.
 9. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) against the adverse cholinergic effects of Galantamine (orally, tablets of 4, 8 or 12 mgs/day or capsules of 8, 16 or 24 mgs/day) in the symptomatic treatment of AD, by their antagonism of the M2 and M3 muscarinic receptors.
 10. Pharmaceutical use of the compounds of the claim 1 (orally, 1 to 10 mgs/day) for the valorization of Galantamine, (orally, tablets of 4, 8 or 12 mgs/day or capsules of 8, 16 or 24 mgs/day) as therapeutic drug against the evolution of AD, by their antagonism of the presynaptic muscarinic M2 autoreceptors in synergy with their selective sigma-1 agonism. 